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Stoichiometric CVD WSi2 Using Alternating SiH4 And WF6 Flows

IP.com Disclosure Number: IPCOM000121230D
Original Publication Date: 1991-Aug-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 1 page(s) / 47K

Publishing Venue

IBM

Related People

Basavaiah, S: AUTHOR [+2]

Abstract

The refractory material tungsten silicide is widely used in polycide technology. Tungsten silicide is deposited using CVD or E-gun evaporation system. The CVD system shows better uniformity and control in WSix composition. Due to the kinetics of the CVD process, SiH4 and WF6 flows always yield lower stress non-stoichiometric tungsten silicide with excess silicon, which imparts higher resistivity to WSi2 structure. To lower the resistivity the structure has to be homogenized by annealing at a much higher temperature of 1000oC. A novel process is described which reduces the limit on the high temperature annealing by depositing stoichiometric low stress WSi2 films.

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Stoichiometric CVD WSi2 Using Alternating SiH4 And WF6 Flows

      The refractory material tungsten silicide is widely used
in polycide technology.  Tungsten silicide is deposited using CVD or
E-gun evaporation system.  The CVD system shows better uniformity and
control in WSix composition.  Due to the kinetics of the CVD process,
SiH4 and WF6 flows always yield lower stress non-stoichiometric
tungsten silicide with excess silicon, which imparts higher
resistivity to WSi2 structure.  To lower the resistivity the
structure has to be homogenized by annealing at a much higher
temperature of 1000oC.  A novel process is described which reduces
the limit on the high temperature annealing by depositing
stoichiometric low stress WSi2 films.

      The process involves the deposition of tungsten silicide using
the reaction between SiH4 and WF6 first.
   2xSiH4 + 2WF6 T 2WSix(s) + 12HF(g) + (4x-6)H2(g)
where x is greater than 2.

      Then SiH4 flow is reduced to zero and WF6 only is allowed to
flow over the deposited tungsten silicide. WF6 reduces the WSix by
the following reaction:
   3WSix + (4x-4)WF6 T 3WSi2(s) + (4x-4)W(s) + (3x-6)SiF4 (g)
where x is greater than 2.

      The excess silicon reacts with WF6 forming volatile silicon
tetrafluoride, little tungsten and the thermodynamically stable
disilicide.  Once the reduction reaction is complete, SiH4 is again
allowed to react with WF6 forming nonstoichiometric silicide.  Then
the excess silicon is r...